Fuel cells are useful for generating electrical power. An electrochemical reaction occurs at a proton exchange membrane. Flow field plates are provided on each side of the membrane to carry reactants such as hydrogen and oxygen to the membrane for purposes of generating the electrical power. The flow field plates in some examples are solid, non-porous plates. Other example fuel cell arrangements include porous plates. There are advantages and drawbacks associated with each type of arrangement.
In solid plate fuel cell arrangements, for example, it is necessary to perform a flow field purge at shutdown to remove liquid water from the flow field channels. During the electrochemical reaction, liquid water is produced as a byproduct and tends to collect in the flow fields on the cathode side. If that liquid water remains there and temperatures drop sufficiently low, it will freeze and interfere with the ability to start up the fuel cell after it has been shutdown.
Typical purge procedures include using an air blower and a hydrogen recycle blower to remove the liquid water. One disadvantage of using such a purge procedure is that it introduces relatively large parasitic loads on the system when the fuel cell is no longer producing electrical power. Other issues associated with usual purge procedures are added system complexities and the risk of drying out portions of the fuel cell stack.
There is a need for a water management arrangement and strategy that reduces or eliminates purge requirements.